Dual motor control



Aug. 26, 1947. c. D. DAVIDSON 2,425,488

DUAL MOTOR CONTROL Filed Aug. 30,*1944 2 Sheets-Sheet l HIS en), ha

ATTORNEYS Aug. 26, 1947.

now/v INVENTOR ATTORNEYS Patented ug. 26, i947 Charles D. Davidson, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a

corporation of Delaware Application August 30, 1944, Serial No. 551,964

16 Claims.

This invention relates to an improved control device for a pair of electric motors adapted to :operate concurrently.

'It is among the objects of the present invention A:to maintain concurrently operating electric mortors in substantial synchronism,

Another object of the present invention is to provide a .CQIltrol device adapted to maintain the operation of a pair of electric motors in substan- 'tial synchronism, said device being further adapt- :ed to stop the operation of both motors when either one of the electric motors predetermignately run ahead of 4the other electric motor.

AFurther objects and advantages of the present invention will be apparentfrom the following delscription, reference being -had to the accompany ing drawings wherein a preferred embodiment of the invention is clearly shown.

All of the objects of the present invention are -accomplished by lproviding a synchronizer control device for aA pair of concurrently operating electric motors, said device comprising a rotatable member for each electric motor, each member being rotatable in accordance with the speed of a respective motor. As long as both of these members rotate in substantial synchronism, indicating that both electric motors are also operating in synchronism, the synchronizer merely operates idly. However, if one of said members rotates ahea'd of the other, this member is adapted to render a speed retarding means effective to reduce the operating speed of its respective motor for purposes of equalizing the speed of both motors. If, for some reason, one of the electric motors persists in running ahead or lagging behind the other, so that the motor speed controlling means, rendered eiective by the synchronizer, cannot provide for synchronized motor operation, then the synchronizer is adapted to eifect the breaking of all of the motor circuits and stop the operation of both motors.

In the drawings:

Fig. 1 is a fragmentary view of an airplane wing and its wing flap with the present invention applied thereto.

Fig. 2 is a view into the cup-shaped container of one form of synchronizer. This view is taken in the direction of the arrows 2-2 of Fig. 4.

Fig. 3 is a fragmentary sectional view taken along th'e line 3 3 of Fig. 2. In this view the switches have been eliminated to permit a clearer showing of the rotating portions of the synchronizer.

Fig. 4 is a sectional view taken along the line Aand in the direction of the arrows 4--4.

Fig. 5 is a detailed sectional View of the rotating parts of the synchronizer.

Fig. 6 is a wiring diagram illustrating the two electric motors, the synchronizer and various electrical devices and their electrical connections comprising the control device of the present invention.

The device of the present invention may be used in connection with' any mechanism or machine having parts to be concurrently operated such as truck gates, engine louvres, wing flaps lor ailerons, airplane landing gears, etc. For the present purpose the invention is shown applied to an airplane for operating the wing flaps or ailerons. Each wing of an airplane is provided with a hinged flap operated during flying or to provide speed retarding means for the airplane during landing. To maintain proper balance it is essential that both wing aps be actuated in unison.

The Fig. 1 of the drawings illustrates a portion of one airplane wing in which a motor driven actuator is provided to operate the-flap. The main wing portion is indicated by the numeral 20 and carries a pivot rod 2| to which the Wing flap '22 is hingedly secured.

The motor driven actuator of the present invention is similar in construction to the one forming the subject matter of the copending application Serial No. 468,47 5, filed by Calvin J. Werner and comprises a reversible electric motor 25 adapted to drive a screw shaft 25 through an electromagnet 2l and speed reducing gearing 28. The electromagnet clutch normally disconnects the motor 25 from the screw shaft 26. Normally the screw shaft is held against rotation by engagement with the movable part 0f the clutch with a brake ring 29. When the motor is energized the electromagnet is simultaneously energized causing the movable part of the electromagnet to be withdrawn from engagement with the brake ring 29 and moved into driving engagement with the engine driven member 92 of the clutch.

The screw shaft 26 is provided with a traveling nut 30 adapted to move from one to the other end of the shaft in response to rotation of said shaft. As the screw shaft 2S is rotated in one direction, the nut 3@ thereon will move outwardly toward the free end of the shaft and as said screw shaft rotates in the opposite direction the nut will move inwardly toward the motor.

In Fig. 1 the actuator comprising the motor 25 and screw shaft 26 is rigidly mounted in the wing 2S. As has been mentioned before, the Wing 2i? has a rod 2l upon which the wing flap 22 is hingedly supported. A clevis 34 is secured to the flap 22. One end of an operating rod 35 is anchored to the clevis, the other end of said lever being attached to the traveling nut 30. When, as shown in Fig. 1, the nut is in position substantially midway of the screw shaft 26, the flap 22 is held in proper aligned or neutral position relatively to the wing 20. However, when the motor rotation causes the nut 30 to move inwardly toward the motor 25, then the connection between the nut and wing flap clevis 34 will move the flap 22 upwardly from the rod 2|. Reverse rotation of the electric motor causes the nut to move downwardly, resulting in a downward movement of the wing flap 22.

In the installation as illustrated, it is essential that both wing flaps be actuated in unison, for if one wing flap would be operated to a greater degree than the other, the plane would be thrown into an unbalanced condition, which is particularly undesirable during landing, at which time the flaps are used to retard plane speed,

Any suitable type of synchronizer may be utilined, however, for purposes of this description,

one form is presented comprising a housing having a lid |0|. Particular reference is being had to the Figs. 2 to 5 inclusive. The lid and housing each have an inwardly extending lug |02 and |03 respectively, one aligning with the other and each being recessed to receive the respective ends of a shaft |04 whereby said shaft is rotatably supported within the housing between the bottom end wall thereof and the lid |0l. Keyed to this shaft |04 so as to be substantially in the center of the housing is a cam disc |05. On each side of said cam disc are provided a plurality of narrow elongated recesses each conforming to the periphery of the cam disc, all equally spaced one from the other. Their bottom wall surfaces taper from a predetermined depth at their clockwise ends (Fig. 2) toward the surface of the cam disc, blending therewith at their counterclockwise ends. The recesses in the upper surface of the cam disc |05 are designated by the numeral |06 and those in the bottom surface of the cam disc by the numeral |01.

A rotatable disc, centrally apertured loosely to fit about the shaft |04, rests upon each side of the cam disc |05. The rotatable disc |08 rests upon the upper surface of the cam disc. This disc |08 has tapering, depending extensions |09 conforming in shape and size to the recesses |00 in the engaged surface of the cam disc. Each tapering extension normally occupies a recess in the adjacent surface of the cam disc. A similar rotatable disc H0 loosely fits about shaft |04 and engages the bottom surface of the cam disc |05. Like disc |08, this disc l0 has tapering extending portions each occupying a corresponding recess in the engaged surface of the cam disc |05 Disc |00 is yieldably urged upon the upper surface of the cam disc |05 by a coil spring ||2 surrounding shaft |04 and interposed between two loose washers ||3 and ||4, the former engaging an annular flange on the shaft, the latter resting upon the upper surface of the rotatable disc |08. A similar spring l5 urges the rotatable disc 0 upon the lower surface of the cam disc |05, this spring I|5 being interposed between two loose washers ||6 and the former resting against the rotatable disc I0, the latter resting upon the inner end surface of the lug |03 of housing |00 when the mechanism is assembled.

Each disc |08 and |I0 is provided with ratchet teeth in its outer peripheral edge, the teeth of disc |08 being designated by the numeral |20, the teeth of disc ||0 being indicated by the numeral |2|. The discs |00 and ||0 are rotated by electromagnet impulsers. Disc |00 is actuated by impulser |22 having a reciprocative dog |23 normally held in its retracted position, but when said impulser is electromagnetically energized, dog |23 is thrust outwardly to exert a pushing effort upon the ratchet |20 cf disc |08 whereby to ro tate said disc |08 counterclocliwise the distance of one ratchet tooth (see Fig. 2). impulser |24 has a reciprocative dog |25 adapted to engage the teeth |2| of the disc ||0 so that when said impulser is energized this disc ||0 is move-d counterclockwise through the distance of one tooth by the movement of the dog |25 of the energized impulser |24. Deenergization of either impulser |22 or |24 permits automatic return of their respective dogs |23 and |25 to normal position in which each will seat in its next adjacent respective ratchet teeth of the respective disc |08 or I0. A spring lock dog |26 is supported within the housing engaging the ratchet teeth of disc |0 and provides means to prevent backward rotation of either disc |08 and |0 and also adding a springloaded drag to the forward movement of the disc As long as discs |00 and ||0 are moving in unison there will be no relative movement between them and the cam disc |05 for their synchronized turning will cause the cam disc |05 and its shaft |04 to turn therewith. However, if disc |08 is rotated faster than disc ||0, its tapered extensions will be moved ahead of the rotation of the cam |05 and will consequently cause them to ride upwardly on the upwardly sloping bottom surfaces of the respective recesses in which said extensions rest. Relative movement between the tapering surfaces of the cam recesses and the occupying disc extensions cause the disc |08 to move longitudinally of the shaft |04 against the effect of spring ||2 whereby the disc |08 will move upwardly in the housing toward the lid |0|. Similarly when and if rotating disc ||0 turns faster than disc |08, a relative movement between disc ||0 and cam disc |05 obtains and the engaging sloping surfaces of the extending portions on disc I|0 and their respective recesses in cam |05 will cause a movement of the disc ||0 longitudinally of the shaft |04 away from the camming element |05 and toward the bottom of the synchronizer housing |00.

The synchronizer provides switches for controlling certain circuits of the device. The Figs. 2 and 4 clearly illustrate these switches. A plurality of insulating collars |30y |3|, |32 and |33 form an insulating post held upon the synchronizer lid |0| by a screw |34. This post supports a plurality of resilient contact blades, the one designated by the numeral |35 being supported between the insulating collars |32 and |33 and the plate |36 being supported between collars |32 and |3| and the plate |31 between collars |3| and |30. Blade |35 carries a contact |38 adapted normally to engage a contact |30 carried by blade |30 which also supports an insulating bumper on each side thereof adjacent its ends, one designated by the numeral |40 interposed between the blade |36 and the rotatable disc |20, the other |4| on the opposite side of blade |36 and adapted to be moved into engagement with blade |31 to move it after blade |36 has been flexed by the movement of disc |20 engaging bumper |40 and moving blade |36 a predetermined distance. Another insulating post is carried by the lid this post comprising insulating collars |45, |45, |41 and |43 held on the lid by screw |43. A spring blade |50 is held between collars |48 and |41, a blade |5| between collars |41 and |45l and a blade |52 between collars |43 and |45. Blade |55 has a contact |53 engaging contact |54 on blade |31. Blade |5| carries a contact |55 normally engaging contact |55 carried by blade |52. An insulating block |51 at the end oi blade |52 normally rests upon the contact blade |31. These contact blades are so arranged that in response to movement of the disc |33 longitudinally of shaft |54 it will engage bumper |40, continued longitudinal movement of the disc |08 relatively to the shaft |54 moving contact blade |35` to separate contacts |33 and |33. If the longitudinal movement of disc |55 relatively to the shaft |34 continues, the movement of blade |3l1` upwardly by said disc |58 will cause the bumper |4| thereon to engage contact blade |31, moving it to separate its contact |54 from the contact |53 on blade |55. Con-- currently with the separation of contacts |53 and |54 by movement of blade |31, abutment block |51 will move contact blade |52 to separate its contact |56 from engagement with contact |55 on blade |5|.

Two insulating posts are supported on the bottom wall of the synohronizer housing |50. One

of these posts comprises insulating collars |5l, |62 and |53 secured to the housing by screw |64. A contact blade |55 is supported between insulating collars |53 and |52. Another contact blade |55 is supported between collars |52 and |5| and a third contact blade |51 is supported between collars |5| and |55. Blade |55 has a contact |58 at its free end normally engaging contact |53 on blade |56. Blade |65 carries an insulating bumper element at its end, engageable by the disc |||l when it moves longitudinally relatively to the shaft |54.

The other insulating post comprises insulating collars |15, |15, |11 and |15 held in stacked relation on the bottom of the synchronizer housing by screw |13. Contact blade |53 is supported between insulating collars |15 and |15. Blade 15| is supported between collars |16 and |11. Blade |82 is supported between collars |11 and |15. Blade |19 has a Contact |83 normally engaging contact |84 carried at the end of blade .l 51, Blade |5| carries a contact |85 at its free end normally engaging contact |55 on blade |52. An abut-l ment insulating block |51 is interposed between the free end of Contact blade |82 and blade |51. As the disc H0 moves downwardly longitudinally of shaft |54 it first engages abutment separating contacts |58 and it. Continued movement of the disc Il@ relatively to the shaft |34 in this direction causes abutment block |53, on the side of Contact blade 55 opposite the abutment block |15, to engage blade |51, moving it to separate contacts |83 and |34 and at the same time moving contact blade |52 by the abutment block |81 to separate contacts |55 and |35.

In the installation of the device of the present invention various electrical devices are provided in the circuits to effect control oi the electric motors. Among these devices are two electromagnetic actuated contactors designated as a whole by the numerals 55 and 255. The co-ntactor 53 controls the circuits of the two motors for operating them in `a direction so that the screw shaft rotates to move the nut downwardly thereon. The co-ntactor 253 controls the cirbleek its, v

cuits of the motors, operating their respective screw shafts so that the nuts thereon move upwardly or in a direction toward the motors themselves. Inasmuch as both of these contactors are identical, only one will be described detailedly.

Referring to the contactor 5|] it is shown comprising a solenoid magnet having a core 5| which carries two bridging elements 52 and 53. An electromagnet winding -54 surrounds the core '5| so that when energized it may actuate the core to move the bridging contacts into circuit closing position. Bridging contact 52 moves into engagement with terminals 55 and y56 and bridging contact 53 s moved into engagement with terminals 51 and 58.

The source of electric power for operating the device of the present invention is a storage battery 535. A master switch 260 may be actuated to bridge contacts 26| and 262 to connect the battery with a selector switch comprising an operating contactor 233 adapted to be moved into engagement with the down terminal 264 or with the up terminal 235. The movable contact member of this selector switch is normally held in neutral position between the two terminals 264 and 265. A holding magnet V266 is provided which may be electrically energized to hold the movable contact member 263 in the down circuit closing position as long as the circuit is maintained through the holding magnet 266 to energize it. A similar holding magnet 261 is provided on the. opposite side of the selector switch to hold movable contactor 253 in the up circuit closing position as long as the electromagnet holding' magnet 251 is maintained energized.

The means for controlling the speed of the. respective electric motors, more specifically the means for reducing the speed of each electric motor comprises a resistance, the one in circuit with the motors when they operate in the direction causing downward movement of their respective nuts being designated by the numeral 210. The resistance unit 21| may be introduced in circuit with one or the other electric motor to control speed when the motors are operating in a direction to move their respective nuts upwardly.

Each motor 25 and 2-25 is adapted to drive a timer mechanism for controlling the operation of their respective impulses |22 and |24 in accordance with the operation of the respective motor. The numeral 15 designates the timer operated by the motor 25, this timer being an electric switch or contactor adapted to be operated to open and close circuits at recurrent equal in-l tervals. A cam 16 on the screw shaft has equally spaced lobes which engage a movable part of the switch at recurrent intervals to actuate it to open and close the timer switch 15. A similar timer switch y215 is opened and closed at equal intervals by a cam i216 on the screw shaft 225 driven by the electric motor 225. Timer switch 15 controls the energizaton of the impulser |22 so that it drives the rotatable disc |08 of the synchronizer in accordance with the speed of the electric motor `25. The timer switch 21'5 controls the energization of the impulser |24 so that it drives the disc in accordance with the operating speed of the electric motor 225.

Any type of limit switches may be applied which are effective to stop operation of the respective motors when their driven nuts reach extreme positio-ns at either end of their respective screw shafts. Such limit switches are diagrammatically shown in the Fig. 6. The limit switch which controls the operation of the electric motor 25 so that.

it will stop when the nut 3|) reaches its uppermost position, comprises contacts 18 and 19 normally engaged but separable by the nut 38 when it reaches its uppermost position. A similar switch comprises contacts 80 and 8| normally engaged is actuated by the nut 36 to separate said contacts when the nut reaches its lowermost position in the screw shaft 26. The opening of either one of the sets of contacts 18-19 or SCi- 8| breaks the electric circuit through the magnet winding 54 of the contacter 50. Similar limit switches are provided in connection with the nut 230 driven by the electric motor 225. The switch comprising contacts 218 and 219 is engageable by the nut 236 when it reaches its uppermost position to break engagement of said contacts and open the circuit through the winding 254 of the contactor 250. This circuit may also be broken by separation of the contacts 280 and 28| by nut 230 when it reaches its lowermost position on the screw shaft 226. Contacts 1819 are connected in series with contacts 21B- 219, and 80-8| in series with contacts 280-28 I.

The electric motor 25 has two iield windings, the one designated by the numeral 85 which when energized causes the motor 25 to rotate the screw shaft 26 so that the nut 3D thereon moves downwardly. The other winding 86 of this motor causes the motor to operate in the o-pposite direction when energized, resulting in an upward movement of the nut on the screw shaft 26. Correspondingly motor 225 has a field 285 which when energized causes the motor 225 to rotate shaft 226 to move nut 230 downwardly while the field 286 causes a reverse rotation of the motor 225 whereby the screw shaft 226 is rotated to move the nut 230 thereon upwardly.

As has been mentioned before, each electric motor is normally disconnected from the speed reducing gearing through which it rotates its respective screw shaft. Each electric motor is provided with an electromagnetic clutch having a movable armature member normally engaging a brake ring to hold the respective screw shalt against rotation normally. When the respective electric motor is energized, its electromagnetic clutch is likewise energized so that the movable armature member thereof is withdrawn from frictional engagement with its respective brake ring and movable into gripping engagement with the motor driven disc. The electromagnetic clutch of the motor 25 comprises a winding 96 which when energized attracts the movable armature portion 9| of the clutch into engagement with the driven disc 92 of the motor. The motor 225 has an electromagnetic clutch comprising a wind-- ing 290 which when energized attracts the movable armature member 28| of the clutch to move it out of engagement with the braking ring 226 and into gripping engagement with the motor driven disc 292. The speed reducing gearing of motor 25 is designated by the numeral 28, and the speed reducing gearing of the motor 225 is designated by the numeral 228.

The operation of the device of the present invention will now be described. If the pilot of the plane equipped with the present invention wishes to land his craft, and in landing wishes to apply braking means to reduce its speed, the wing aps 22 will be lowered to provide impedance to air ow past the wings and thereby reduce the speed of the vehicle. The preliminary operation requires the closing of the master switch 260 to bridge contacts 26|-262 and connect the storage battery 500 with the selector switch contact 263,

To lower the wing flaps 22 the pilot actuates the movable contact 263 of the selector switch counterclockwise out of its neutral position so as to engage the terminal 264 of the selector switch. Now the following circuit will be established:

From the battery across terminals 26| and 262 of switch 260, through the movable contact 263 of the selector switch to terminal264 thence to the holding magnet 266 through wire 300 to the switch blade |31 of the synchronizer across contacts |54 and |53 through the blade |58, wire 30| to blade |82 across contacts |86 and |85, blade |8| back to the storage battery via the ground connections. Now the holding magnet 266 is energized and as long as this circuit is maintained the movable contact 263 of the selector switch will be held in this circuit closing position.

As soon as the terminal 264 is engaged by the selector switch, current will flow from battery through the co-ntact 263 and terminal 264 into and through wire 302 through the magnet winding 54 of the contactor 50, wire 383 across the contacts 88 and 8| of the down limit switch of the motor 25 thence through wire 304 across contacts 28| and 280 of the down limit switch of the motor 225 and back to the source of electric power or storage battery 568 va the ground connection. Energization of the magnet winding 54 will cause attraction of the core 5|, moving it so as to bring the bridging members 52 and 53 thereof into engagement with their respective terminals of the contacter. Now the following circuit from the storage battery is completed: from the battery to the junction point 305, thence through the wire 366 to the junction point 301 thence through the short circuiting path including wire 308, synchronizer contact blade |36, contacts |39 and blade thence through wire 309 to the terminal 55 of the contacter across the bridging member 52 to terminal 56 thence through wire 3H), field winding 85 through wire 3|| across the armature of motor 25 through a temperature responsive protective device 3|2 back to the battery via ground connections. The wire 3|l also connects with the magnet winding 90 of the electromagnetic clutch which is also connected with the protective device 3|2 so as to lead to ground therethrough. Another wire 3|4 leads from the junction point 505 to the contact blade of the synchronizer and current flow therethrough will pass through the engaging contacts |68 and |69 through blade |66, wire 3|5 to the junction point 3|6 thence through wire 3|1 to the stationary terminal 58 of the contacter 50 across the bridging element 53 to terminal 51 thence through wire 3|8 to the eld 285 of the motor 225 thence through wire 3I9 through the armature of the motor 225 and protective device- 320 to ground and also through the magnet winding `28|) of the electromagnetic clutch through the protective device 329 to ground.

With these circuits completed and current iiowing through both fields 85 and 285 of the electric motors 25 and 225 respectively and also through the magnet windings and 290 of their respective electromagnetic clutches, the motors 225 will operate to turn their respective screw shafts 26 and 226 in a direction in which their respective nuts 30 and 230 will be moved downwardly or toward the free end of said screw shafts. As these nuts 30 and 230 move in this direction their connections with the respective wing flaps, the one shown being designated by the numeral 35 for the link and 22 for the flap, will cause said 9 flaps to be moved downwardly or clockwise for air brake purposes.

Current flowing through the wire 306 will also flow from the junction 320 through wire 32|, magnet winding of the pulsator |24 through wire 322 down to and across the timer switch 215 back through ground connection to the battery 550. Current will also flow from the junction point 323 in wire 3M through wire 324, magnet winding of the impulser |22 thence through wire 325 to and across the timer switch 15 and back to the battery via ground connections.

t has previously been stated that timer switches 15 and 215 are driven by cams 15 and 216 on the shafts 26 and 226 of the motors 25 and 225 respectively. These timer switches are operated to open and close their respective circuits at equal intervals in recurrent sequence. Thus when the motor 25 rotates screw shaft 25, switch 15 will repeatedly close and open the circuit through the impulser |23 at equal intervals, attracting and releasing its actuating member |23 at such equal intervals. The operation of the actuator |23 of impulser |22 will thus move the rotatable disc |08 through the distance of one tooth or ratchet as provided thereon, each time the impulser is energized and deenergized. Thus it may be seen that this disc |03 will be rotated in accordance with the operating speed of the motor 25. Likewise timer switch 215 closing and opening its circuit at equal recurrent intervals in accordance with the speed of the electric motor 225 will cause energization and deenergization of the magnet winding of the impulser |25, thus each time the impulser |24 is deenergized, its actuator |25 is moved inwardly to move it back into engagement with the 'next adjacent following tooth and when the impulser is energized its actuator |25 will be moved outwardly to rotate the disc H6 through a distance equal to the space of a ratchet tooth thereon. Consequently disc |||l is rotated in accordance with the speed at which the electric motor 225 is operating.

As long as the motors 25 and 225 rotate at substantially the same speed, their timer switches 15 and 215 respectively will cause impulsers |22 and |24 to operate in synchronism and therefore these impulsers will rotate their respective discs |52 and I at substantially the same speed. While these discs 68 and i6 are rotating at substantially the same speed, their extending portions |09 and I respectively, seating in the respective recesses |09 and |01 of the disc cam, will cause said disc cam |95 to rotate with both discs |08 and lill. While discs |58 and il@ are rotating in unison with the cam disc |65, the synchronizer may be said to be operating idly and no control is effected thereby. However, should the one motor operate at a faster rotating speed than the other, then this synchronous or idle movement of the synchronizer is upset and controlling efforts will be instituted. For instance, if the electric motor 25 operates at a greater rotating speed than the electric motor 225, the timer switch 15 actuated by the motor will make and break its circuit at a greater speed than the timer 215 driven by the electric motor 225 now operating at lesser speed than the motor 25. As a consequence the impulser |22 -will be more rapidly energized and deenergized than the impulser |24 and therefore disc |08 will be rotated at a greater speed than the disc ||0 rotating in accordance with the rotating speed of its associated motor 225. As the disc |08 rotates faster than the disc ||0 or the cam whose rotating speed is controlled by the rotation of the slower rotating disc, the sloping surface of the extensions |09 on disc |08 will start to move relatively to the sloping bottom surface of the recess |06 occupied by said extensions and therefore as disc |08 rotates counterclockwise as regards Fig. 2 it will also move upwardly longitudinally of the shaft |04 or more specically away from the cam disc 65. In response to this longitudinal movement of disc |08 the abutment insulating block |40 is engaged and contact blade |36 is moved upwardly to separate the contacts |38 and |39. With the breaking of these contacts the short circuit around the resistance unit 210, which short circuit includes the wire 308, contact blade |36, contacts |39 and |38 and blade |35 is opened and therefore the main current flow to the iield of motor 25 has the resistance unit 210 inserted therein. With the introduction oi this resistance unit 210 into the motor eld circuit the motor speed will be reduced so that eventually it will operate at substantially the same speed as the other electric motor 225.

If the introduction of the resistance unit 210 in the iield circuit of motor 225 does not eventually equalize operation between the two motors, or more specifically, if the motor 225 still tends to lag behind the operation of motor 25, then the disc |08 is still rotated ahead of disc 0 and continued longitudinal movement of the disc |03 relatively to the shaft |04 will obtain. At a predetermined point in this continued longitudinal movement of disc |08 the abutment block |4| on contact blade |36 will engage contact blade |31 and move it upwardly, iirst to break engagement between contacts |53 and |54 and at the same time move contact blade |52 through the abutment block |51 to separate contacts |55 and |56. Separation of contacts |53 and |54 breaks the circuit established through the holding magnet 266, causing its deenergization, at which time the movable contactor arm 263 of the selector switch is released and automatically returned to neutral position. This breaks the circuit to the magnet winding 54 of the controller 50, deenergizing it and permitting its return to normal position in which the bridging elements 52 and 53 are moved out of contact with their respective terminals 55-56 and 51-53. As a result of the movement of the bridging members 52 53 out of engagement with their terminals the motor circuits through fields 85 and 285 are discontinued and motor operation will cease.

Now for instance if the motor 225 rotates at a greater rate than motor 25, then its timer 215 will cause operation of its respective impulser |24 to turn the disc ||0 ahead of disc |06. In response to the faster rotation of disc H0, its extensions acting on the cam |05 will cause longitudinal movement of the disc ||0 relatively to the shaft |04 against the effect of spring ||5 and consequently the abutment block |10 will be engaged to move contact blade |66 and break contacts |68 and |60.

Separation of contacts |68, |69 destroys the short circuit around the regulating resistance 21| and therefore introduces it into the circuit of the motor eld 285, reducing the speed of operation of motor 225. If the resistance 21| is not eifective to establish synchronous motor operation and if unequal motor operation persists, then the disc H0 will continue in its longitudinal movement due to its being driven at a faster rate than disc |50 and at a predetermined point an abutment block |88 on blade |66 will engage blade |61 to separate contacts |83 and |84 and also to separate contacts M and |55 by shifting of the contact blade Si Separating contacts |55 and |55 breaks the circuit through the holding coil 256 and causes its deenergization. It will be seen that contacts |85 and |56 are in series with the contacts |53 and |54 which are connected by wire 300 to the holding coil 255. Deenergization of electromagnet holding coil 255 by breaking of contacts |85 and |56 will have the same effect as before, that is it releases the movable contact arm 253 of the selector switch to move to neutral position where the terminal 254 is no longer engaged and thus the circuit through the magnet winding 54 of the contactor 55 is broken, thereby permitting the contactor to open the motor circuits and terminate motor operation.

The above description has been directed to the operation of the motors in a direction in which their respective screw shafts rotate to move the nuts downwardly. When the pilot wishes to move the wing flaps upwardly, he actuates the movable contactor arm 253 of the selector switch clockwise to engage terminal 255 whereby to establish a circuit through the holding coil magnet 261 and through the contactor 255. As soon as the contactor 255 is energized so that its winding 254 attracts the core 25| to cause bridging elements I5L-253 to engage their respective stationary terminals Z55-255 and 25?-258 respectively the following motor circuits are established:

From the storage battery 55D to the junction point 355 through wire 30S to junction point 301, wire 358, across contacts IRB-|38, wire 359 to the junction point 3I3, thence through wire 350 to the stationary terminal 256 of the contactor 250 across bridging element 25| to terminal 255, wire 35| through the winding 8B of the motor 25 thence through the motor armature and the winding Si) of the electromagnetic clutch to ground whereby motor 25 operates in a direction to rotate its screwshaft 26 so that the nut 3D will move upwardly thereon toward the motor. Current will also flow from the junction point 305 through wire 3I4 across contacts IEBAISS, Wire SI5 to junction point 3I6 thence through wire 354, terminal 258, element 253, terminal 251 down through the winding 285 of motor 225 thence through the motor armature and also the magnetic clutch winding 29|) back to the battery via ground. Energization of field 295 will cause the motor 225 to rotate so that its screw shaft 225 is turned, causing the nut 230 thereon to move upwardly toward the motor. The direction of rotation of the motor 25 and 225 does not alter the effect or" the timer switches and 215 respectively or the synchroniser. If when rotating in the direction just described the motor 2'5 operates at an excessive speed, the synchronous disc |08 will be operated to introduce the regulator resistance 21|) into its circuit. If on the other hand the motor 225 operates faster than the motor 25, the timer switch 215 and impulser |24 will effect rotation oi the synchronous disc III) ahead of the disc |08 whereby longitudinal movement of the synchronous disc I I0 is effected and the regulating resistance 21| is introduced into the circuit of the motor 225 to reduce its speed. The synchronizer will also act to stop operation of both motors if either one of them persist in continued movement ahead of the other.

Limit switches are provided on each motor for limiting the extreme movement of the nuts actuated thereby. On motor 25 the limit switch comprises contacts 18 and 19 and on motor 225 the limit switch comprises contacts 218-219. These switches are connected in series with each other and with the magnet winding 254 of the contactor 250 so that when the nuts reach their extreme upper position these limit switches are opened to break the circuit through the winding 254 of the contactor 250, thus causing its deenergization and effecting the breaking of the motor circuit. Likewise limit switches including contacts and 8| adjacent nut 30 of motor 25 and a limit switch including contacts 280 and 25| engageable by the nut 230 actuated by motor 225 are adapted to be opened when the respective nuts reach their lowermost position. When these two limit switches are opened they, being in circuit with the magnet winding 54 of the contactor 55 will break this circuit, causing deenergization of this contactor and causing it to break both motor circuits and stop motor operation.

From the aforegoing it may clearly be seen that applicant has provided a control device for two electric motors adapted to operate concurrently, said control functioning substantially to maintain synchronous operation of the motors. The control device is further adapted to discontinue motor operation if for any reason one motor persists in lagging behind or one motor persists in running faster than the other motor, thereby avoiding any damage which might occur if the condition causing unequal motor operation is permitted to continue.

While the embodiment of the present invention constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

l. In a control device for a plurality of electric motors radapted to operate concurrently, the combination with a source of power, of a switch for simultaneously connecting all of the motors with the source of power; separate, normally ineiective speed controlling means for each motor; a unitary synchronizer comprising a plurality of cooperating elements each one of which is operated in accordance with the speed of a respective motor, each element being adapted to render a speed controlling means effective in response to rotation of the associated motor in excess of the speed of another motor; and an impulser controlled by each motor to effect operation of the synchronizer elements in accordance with the speed of the respective motor.

2. In a control device for a plurality of electric motors, the combination with a source of electric power; means for simultaneously connecting all of the motors with the power source for concurrent operation of all of the motors; normally inefiective speed controlling means for each electric motor; a synchronizer comprising separate relatively rotatable members, each adapted to be rotated in one direction in accordance with the rotating speed of a respective electric motor, said synchronizer comprising also an element adapted to shift either one of said members to render a speed controlling means effective to control the speed of the electric motor associated therewith when said one member rotates at a faster rate than the other; and means for rotating said synchronizer members in accordance with the speed of a respective electric motor.

3. In a control device for a plurality of electric motors adapted to operate concurrently, the combination with a source of power, of a switch for simultaneously connecting all of the motors with the source of power; a normally ineffective speed regulating winding adapted to be connected in the circuit of each electric motor; a synchronizer normally ineiiective but adapted, in response to unequal speeds of the respective electric motors, to control the speed of the fastest operatingT motor by rendering effective the speed regulating winding connected therewith; and means controlled by each electric motor for eifecting operation of the synchronizer in accordance with the speed of the respective motor driving said means.

4. In a control device for a plurality of electric motors adapted to operate concurrently, the combination with a source or power, of a switch for simultaneously connecting all of the motors with the source of power; a normally short circuited resistance winding in circuit with each electric motor; a synchronizer ineffective while all of the electric motors are operating at substantially the same speed, said synchroniser being adapted to break the short circuit about a resistance winding and render it effective to retard the speed oi the motor connected therewith in response to speeds thereof in excess of the other motors; and means controlled by each electric motor for effecting operation of the synchronizer in accordance with the speed oi the respective electric motor operating said means.

5. In a control device for a plurality of electric motors adapted to operate concurrently, the combination with a source of power; of a switch for simultaneously connecting all of the motors with the source of power; a separate, normally short circuited resistance winding in circuit with each electric motor; a synchronizer operating idly while all of the electric motors are operating in substantial synchronism, said synchronizer being adapted to operate eiectually to render one of the resistance windings effective to reduce the speed of the particular motor connected thereto in response to increase in operating speed of said particular motor over the other motors; electromagnetic means for actuating the synchro-nicer; and a timer switch operated at regular intervals by said electric motor, each timer switch controlling the ener-gization of an electromagnetic means in accordance with the speed of the respective motor.

6. In a control device for a plurality of electric motors adapted to operate concurrently, the combination with a source of power, of a switch for simultaneously connecting all of the motors with the source of power; a normally inactive, speed regulating device for each electric motor; a controller for each of said speed regulating devices; means for operating each controller in accordance with the speed of a respective electric motor; and means engaging all of said controllers, adapted to maintain said controllers ineffective to render their respective speed regulating devices active while said controllers are operating in unison, but adapted to render a speed regulating device active to retard the operating speed of its motor in response to unequal rotation of the electric motors.

7. In a control device for two concurrently operating electric motors, the combination with a source of electric power; of a switch for simultaneously connecting both motors with the power source; normally inactive speed controlling means for each motor; a synchronizer comprising two rotatable discs each adapted to be shifted to render a speed controlling device active; a device interposed between said discs, normally having no effect upon said disc, but adapted to shift one disc to render its speed controlling device active when said one disc is rotated at a greater speed than the other; and means Linder the control of each electric motor for rotating a respective disc in accordance with the operating speed of the controlling motor.

8. In a control device for two concurrently operating electric motors, the combination with a source of electric power; of a switch for simultaneously connecting both motors with the power source; normally inactive speed controlling means for each motor; a synchronizer comprising two rotatable discs adapted to be shifted axially to render one or the other speed controlling device active; a camming device interposed between and engaging said discs and adapted to act as a discY shifting device only in response to the rotation of one disc at a greater speed than the other; separate means for imparting rotative impulses to each disc in recurrent sequence; and means operated at equa-l intervals by each motor for effecting energization of the respective impulse imparting means.

9. In a control device for two concurrently operating electric motors, the combination with a source of electric power; of a switch for simultaneously connecting both motors with the power source; normally inactive .speed controlling means for each motor; a synchronizer comprising two rotatable discs adapted to be shifted axially to render one or the other speed controlling device active; a camming device interposed between and engaging said discs and normally ineffective to shift either disc axially while said discs are rotating in unison, but adapted to shift a disc axially when it rotates at a greater rate than the other; an electromagnetic actuator for rotating each disc; and means actuated by each motor to effect operation of a respective electromagnetic actuator in accordance with the rotating speed of the driving motor.

10. In a control device for two electric motors, the combination with a source of electric power; of a switch for simultaneously connecting both motors with the source of power for concurrent operation of said motors; a resistance element in circuit with each electric motor for reducing the maximum operating speed; means for short circuiting each resistance element normally to render it ineffective; a synchronizer comprising two rotatable discs each capable of axial movement to open a short circuit means; a camming device interposed between said discs and engaged thereby and rotatable therewith; a spring for urging each disc into engagement with the camming device; means for rotating each disc; and means actuated by each motor for efecting rotation of a disc in accordance with the speed of the respective electric motor, the camming device becoming effective to move one disc axially to engage and break the resistance element short circuit of the respective motor which is rotating said one disc at a greater speed than the other disc is being rotated by its motor.

1l. In a control device for two electric motors, the combination with a source of electric power; of a switch for simultaneously connecting both motors with the source of power for concurrent operation of said motors; a resistance element in circuit with each electric motor for reducing its maximum operating speed; means for short circuiting each resistance element normally to render it ineffective; a synchronizer comprising a shifter cam; two ratchet wheels, each yieldably urged upon one side of the cam, said ratchet wheels when rotating in unison, turning the cam therewith, however, when one ratchet wheel rotates faster than the other, said cam will move said faster rotating wheel axially to engage and open a resistance short circuiting means rendering it eiective to reduce the operating speed of the motor connected therewith; an electromagnetically operated ratchet exerting repeated turning impulses upon a ratchet wheel at equal intervals; and a timer switch actuated by each electric motor for recurrently connecting a respective ratchet magnet with the source of electric power.

12. In a control device for two electric motors, the combination with a source of electric power; of a switch for simultaneously connecting both motors with the source of power for concurrent operation; electromagnetic holding means rendered effective to hold said switch in circuit closing position when said switch is closed; a speed reducing resistance connected in series with each motor; means normally short circuiting eac sistance to render it ineffective; a synchronizer comprising a cam; two rotatable discs yieldably urged upon said intermediate cam adapted to shift one or the other disc axially only when said discs are not rotating in unison whereby said axially moving disc engages and breaks the short circuiting means of an electric motor; two normally closed means in circuit with the said holding means, each' adapted to be actuated by a respective synchronizer disc to deenergize the holding means and effect its release of the switch whereby the motor circuits are discontinued when said synchronizer disc is moved axially into a predetermined position; means for rotating said synohronizer discs, each in accordance with a respective electric motor.

13. In a control device for two electric motors, the combination with a source of electric power; of an electromagnetic controller switch adapted to be actuated, simultaneously to connect both motors with the source of power; a hand switch for connecting the electromagnet switch with the source of power to energize it for closing the motor circuits; a holding magnet rendered elective to hold the hand switch in operated position by the closing of said hand switch; a speed reducing resistance in each motor circuit; means normally rendering each resistance ineffective; a synchronizer having separate parts each operated under the control of and in accordance with the speed f a respective electric motor, said parts operating idly when acting in unison in response to equal rotating speeds of the respective motors but adapted to be shifted axially to render one or the other speed reducing resistances effective when one of the motors rotates at a greater speed than the other, whereby the faster operating motor is retarded; means for rotating said synchroniser parts; and circuit controlling means connected in series with the holding magnet, each adapted to be actuated by a respective synchroni er part to open its circuit and release the hand switch for deenergizing the controller switch and break both motor circuits when said synchro' incr part has been shifted nlly to a predet mined position by continued dual rotation of the electric motors.

141. In a control device for a plurality oi reversible electric motors, the combination with source of electric power, controllers for simultaneously connecting all motors to the source of power, one controller for concurrent operation of the motor in one direction, the other for concurrent motor operation in the opposite direction; means normally ineiective but adapted to be rendered effective to reduce the speed of each electric motor in either direction; a. synchronizer having separate, relatively rotatable members each adapted to be rotated in one direction in accordance with the rotating speed of an electric motor in either direction; means actuated by one of said members when it is rotating faster than the other member for rendering effective the speed reducing means of the electric motor with which said faster rotating member is synchronized; and means for rotating each synchronizer member in accordance with the speed oi respective motor.

l5. A device accordance with claim 14 in which, however, circuit controlling means are provided, adapted to be actuated by either member of the synchronizer when one of said members is rotated predeterminately ahead of the other member for disconnecting all of the electric motors from the source of power.

1G. In a control device for two electric motors adapted to be connected to a source of electric power for concurrent operation; means adapted concurrently to connect said two motors with the power source; speed governing means for each electric motor; a synchronizer having moving parts, ineffective when moving in synchronism, but effective to render one or theother speed governing means effective in response to unsynchronized movement of said parts; impulsers for each of said synchronizer moving parts, adapted to provide equally timed, recurrent moving impulses to a synchronizer part; and a timer actuated by each electric motor, each adapted to render an impulser eiective to deliver its impulses to its respective synchroniser part in accordance with the rotating speed of its driving motor.

CHARLES D. DAVIDSON.

REFERENCES CITED UNITED STATES PATENTS Name Date Menzies Nov. 2, 1926 Number 

